To meet the demand for higher integration density and operating speed of LSIs, the effort to reduce the pattern rule is in rapid progress. The wide-spreading flash memory market and the demand for increased storage capacities drive forward the miniaturization technology. As the advanced miniaturization technology, manufacturing of microelectronic devices at the 65-nm node by the ArF lithography has been implemented in a mass scale. Manufacturing of 45-nm node devices by the next generation ArF immersion lithography is approaching to the verge of high-volume application. The candidates for the next generation 32-nm node include ultra-high NA lens immersion lithography using a liquid having a higher refractive index than water in combination with a high refractive index lens and a high refractive index resist film, EUV lithography of 13.5 nm wavelength, and double patterning version of the ArF lithography, on which active research efforts have been made.
The exposure system for mask manufacturing made a transition from the laser beam exposure system to the EB exposure system to increase the accuracy of line width. Since a further size reduction becomes possible by increasing the accelerating voltage of the electron gun in the EB exposure system, the accelerating voltage increased from 10 kV to 30 kV and reached 50 kV in the current mainstream system, with a voltage of 100 kV being under investigation.
As the pattern feature size is reduced, approaching to the diffraction limit of light, light contrast lowers. In the case of positive resist film, a lowering of light contrast leads to reductions of resolution and focus margin of hole and trench patterns.
As the pattern feature size is reduced, the edge roughness (LWR) of line patterns and the critical dimension uniformity (CDU) of hole patterns are regarded significant. It is pointed out that these factors are affected by the segregation or agglomeration of a base polymer and acid generator and the diffusion of generated acid. There is a tendency that as the resist film becomes thinner, LWR becomes greater. A film thickness reduction to comply with the progress of size reduction causes a degradation of LWR, which becomes a serious problem.
The EUV lithography resist must meet high sensitivity, high resolution and low LWR at the same time. As the acid diffusion distance is reduced, LWR is reduced, but sensitivity becomes lower. For example, as the PEB temperature is lowered, the outcome is a reduced LWR, but a lower sensitivity. As the amount of quencher added is increased, the outcome is a reduced LWR, but a lower sensitivity. It is necessary to overcome the tradeoff relation between sensitivity and LWR. It would be desirable to have a resist material having a high sensitivity and resolution as well as improved LWR and CDU.
Phenolphthalein opens its ring in alkaline water to generate a carboxyl group to thereby increase an alkaline dissolution rate. Utilizing this mechanism, Patent Document 1 proposes a positive resist composition comprising phenolphthalein. Patent Document 2 proposes a positive resist composition comprising phenolphthalein whose phenolic hydroxyl group is substituted with an acid labile group.
Patent Document 3 proposes a chemically amplified resist composition comprising a metal salt of carboxylic acid. The metal salt of carboxylic acid undergoes anion exchange with fluorosulfonic acid generated by an acid generator upon light exposure. That is, from the metal salt of carboxylic acid and fluorosulfonic acid, a metal salt of fluorosulfonic acid is formed and carboxylic acid is released. Since the metal salt of fluorosulfonic acid is neutral, it does not provoke deprotection reaction. This means that the metal salt of carboxylic acid functions as a quencher for fluorosulfonic acid. Since the metal has a higher molecular weight than hydrocarbons and is more effective for suppressing acid diffusion, the metal salt functions as an improved quencher.